The invention relates to an internal combustion engine with an engine block and a cylinder head, between which a cylinder head gasket is disposed, and a piston arranged in a cylinder having a cylinder surface with cylindrical ring disposed between the piston and the cylinder surface.
In modern internal combustion engines, particularly Diesel engines, it is necessary to provide sufficient play for the top land of the piston so that, at the operating temperature and the corresponding expansion of the aluminum piston, no contact occurs between the top land of the aluminum piston and the surrounding cylinder wall. The top land of a piston is the area between the uppermost piston ring, which is closest to the cylinderhead and the upper edge of the piston.
Especially with the use of synthetic oils for the lubrication of the internal combustion engine, there is the disadvantage that hard deposits are formed by combustion of the synthetic lubricant, which build up in the area of the top land and which finally contact the cylinder surface. During the reciprocating movement of the piston the hard deposits may then destroy the hone structure formed into the cylinder walls during manufacture. Then the cylinder surface loses the surface structure required for retaining a sufficiently thick lubricating oil film on the cylinder surface, which results in a high lubricating oil consumption and faster wear of the cylinder and the piston.
To avoid those effects, a cylindrical ring is being inserted in the area of the cylinder surface adjacent the cylinder head, that is, a recess is provided in the cylinder wall adjacent the cylinder head for receiving such a ring. The cylindrical ring projects from the cylinder wall surface and causes dislodging of the deposits in the area of the top land of the piston.
Such an arrangement is disclosed in principle in DAS 1 902 502. Furthermore, U.S. Pat. No. 5,553,585 describes a complex embodiment of such a ring arrangement.
It is however a disadvantage that such a ring requires space in radial direction which results in increased engine volume: For manufacturing reasons, the cylindrical ring has to have a certain wall thickness in order to be stable and to facilitate handling during assembly.
This is especially critical if the wall thickness behind the cylinder surface is already very small since for example a cylinder sleeve is inserted. In this case, high material tensions occur and a notch effect is generated in that area in which the cylinder sleeve has a very small wall thickness.
It is therefore the object of the present invention to provide an internal combustion engine with a cylindrical ring which provides for a gap between the top land of a piston and the respective cylinder wall surface. The cylindrical ring should require only minimal space in radial direction of the cylinder.